This invention relates to a water wheel operation control method and an apparatus therefor, and particularly to a water wheel operation control method and an apparatus therefor in which when a state of emergency occurs during a power generating operation and a guide vane will not close, the inlet valve is maintained substantially open to a certain degree for a predetermined time period without immediately being closed, thereby preventing the abnormal increase or decrease of water pressure and so on caused upon cut-off of flow.
In this specification, the term "a water wheel" includes not only a water wheel or water turbine but also a reversible pump turbine.
Such a state of emergency can be caused for example by, lightening strokes, abnormal operating conditions of a water wheel and so on. When such a state of emergency occurs, it is necessary to immediately electrically disconnect the load connected to the water wheel. Besides, the operation of the water wheel will have to be stopped in case of the abnormal conditions of the water wheel per se. When the operation of a water wheel is stopped, the guide vane of the water wheel is usually automatically closed. In the case where the guide vane is not closed for some reason such as a failure of a guide vane driver of the water wheel, however, the inlet valve for the wheel is closed. In this case, when the inlet valve is being closed, or in the transient state in which the flow is being cut off, an abnormal water pressure is caused in the water channel or waterway, and this may lead to breakdown of the water wheel or water channel.
In the case of operating a plurality of water wheels which are connected in parallel between the common upper pond or surge-tank and the common lower pond to form a closed loop of waterway therebetween, when, for example, two of the plurality of water wheels have to be simultaneously disconnected from a power system, and when the guide vanes thereof are closed at different times or one of the guide vanes is closed but the other is not closed, the two water wheels may interfere with each other, causing an abnormal water pressure by which the water wheels, or water channels, or waterways may be damaged.